The invention relates to the field of intravascular delivery systems, and more particularly to molds for forming balloons.
In percutaneous transluminal coronary angioplasty (PTCA) procedures to treat a stenosis in an artery, a guiding catheter is advanced until the distal tip of the guiding catheter is seated in the ostium of a body lumen, such as a coronary artery. A guide wire, positioned within an inner lumen of a dilatation catheter, is first advanced out of the distal end of the guiding catheter into the patient""s coronary artery until the distal end of the guide wire crosses a lesion to be dilated. Then the dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient""s cardiovascular system, over the previously introduced guide wire, until the balloon of the dilatation catheter is properly positioned across the lesion. Once properly positioned, the dilatation balloon is inflated with liquid one or more times to a predetermined size at relatively high pressures (e.g. greater than 6 atmospheres) so that the stenosis in a blood vessel is compressed against the arterial wall and the wall expanded to open up the passageway. Generally, the inflated diameter of the balloon is approximately the same diameter as the native diameter of the body lumen being dilated so as to complete the dilatation but not overexpand the artery wall. Finally, the balloon is deflated, blood flow resumes through the dilated artery, and the dilatation catheter can be removed therefrom.
After angioplasty procedures, restenosis may form in the artery at the original stenotic site, necessitating either another angioplasty procedure, or some other method of repairing or strengthening the dilated area. To reduce the restenosis rate and to strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. Stents may also be used to repair vessels having an intimal flap or dissection or to generally strengthen a weakened section of a vessel. Stents are usually delivered to a desired location within a coronary artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter, and expanded to a larger diameter by expansion of the balloon. The balloon is deflated to remove the catheter and the stent left in place within the artery at the site of the dilated lesion.
In the design of catheter balloons, the balloon shape and length must be tailored to provide optimal performance for a particular application, whether it be angioplasty, stent delivery, or other application. In many cases, it may be desired to produce balloons of different lengths but with similar diameters and tapers. Balloons adapted to a particular purpose may be produced in several lengths to accommodate different patient characteristics and physician preferences.
The manufacture of catheter balloons is a delicate and expensive undertaking. Typically, molds of the desired shape and size are created for each balloon design to be manufactured. Such molds are difficult and expensive to produce. In addition, each time it is desired to manufacture a different balloon catheter, time and labor must be expended in changing molds. Accordingly, there is need in the art for catheter balloon molds adaptable for use in the manufacture of multiple balloon designs so as to reduce the cost and improve the efficiency of processes for the manufacturing of inflatable members, such as balloon catheters.
The invention is directed to adjustable length mold assemblies for forming inflatable members for medical devices and methods for using adjustable length mold assemblies for forming inflatable members, such as, for example, balloons for use with balloon catheters and stent delivery systems. In a particular aspect, the invention is directed to mold assemblies for forming such balloons, each mold assembly being effective to form a variety of balloons of a variety of lengths. In another aspect, the invention comprises adjustable length mold assemblies with first mold pieces configured to form working lengths of balloon portions of inflatable members and second mold pieces configured to form tapered end sections of balloon portions of inflatable members.
The adjustable length mold assemblies of the invention for forming inflatable members for medical devices comprise a first mold piece having a first internal chamber defined at least in part by a first internal molding surface configured to form a first exterior surface of a first section of an inflatable member formed in the mold, and a second mold piece having a second internal chamber defined at least in part by a second internal molding surface configured to form a second exterior surface of a second section of the inflatable member formed in the mold, at least a portion of an outer surface of said second mold piece being configured to be slidably received by at least a portion of the first internal chamber of the first mold piece. The second mold piece may be moved so that at least a portion of the second mold piece may assume any one of a plurality of positions within the first mold piece. Inserting a portion of the second mold piece into the first mold piece complements and completes the first internal molding surface to form a variable-length chamber for molding inflatable members for medical devices.
A molding surface that complements and completes another molding surface is one that, together with the other molding surface, forms a complete molding surface having no gaps or discontinuities large enough to prevent the formation of inflatable members for medical devices.
An internal molding surface is an interior face of a bore in a mold. An exterior surface of a section of an inflatable member is the outside surface of an inflatable member, such as a balloon. A surface that is configured to correspond to an exterior surface of a section of an inflatable member is a surface that is the size and shape of a balloon that is to be formed by the mold. Thus, an internal molding surface configured to correspond to an exterior surface of a section of an inflatable member formed in a mold comprises the interior face of a bore in a mold that is the size and shape of the outside surface of a balloon that is to be formed by the mold.
For example, the working surface is an exterior surface of an inflatable member which comprises the longitudinal wall of the balloon portion of an inflatable member for a medical device, and is typically cylindrical in shape. The tapered end section is another exterior surface of an inflatable member, comprising a wall connecting the tube portion with the working surface of a balloon, the wall making an angle with respect to the tube portion of the balloon. A tapered end section typically has the shape of a section of a cone, the wall typically not being perpendicular to the tube. In addition, the tapered end section may comprise multiple portions formed at different angles to the axis of the tube.
It will be understood that, for example, the second mold piece, comprising a movable piece configured to be slidably received by the internal chamber of first mold piece may be a constituent of a group of pieces such as a second mold group, and is not restricted to a unitary second mold piece. Thus, embodiments of the invention may also include a second mold group comprising a support or extension configured to engage and hold a second mold piece having an exterior surface configured to be slidably received by the internal chamber of the first mold piece.
The diameter and shape of the variable-length chamber is defined by the size and shape of the bores of the mold pieces. The length of the variable-length chamber is defined by the length of second mold piece inserted into the first mold piece, and so may be varied over a plurality of lengths. The length of the variable-length chamber determines the length of the balloon of the inflatable member produced in the mold assembly. It will thus be understood by one of ordinary skill in the art that one adjustable length mold assembly may be used to form balloons of a variety of lengths, by adjustment of the length of the variable-length chamber through adjusting the distance that one mold piece is inserted into another mold piece.
The adjustable length mold assemblies of the present invention may further include a positioner effective to place an inner piece in a desired location within the bore of an outer piece.
The molds of the present invention may also have a locking mechanism to secure and retain the mold pieces in a desired position, effective to maintain the mold pieces and the chamber defined by them in position. Locking mechanisms may comprise, for example, a device selected from the group consisting of a screw, a sleeve, a stop, a brake, a gear, a pin, and a clamp.
The cross-sectional shape of the molds of the invention may be substantially circular, or elliptical, or lobed, or any other desired shape. A xe2x80x9csubstantially circularxe2x80x9d shape is one that is circular to within normal variations encountered in manufacture of a mold. Where the cross-sectional shape is elliptical, the lengths of different radii may of course vary at different angular orientations around a longitudinal axis of the mold. Similarly, where the mold is lobed, lobes need not be identical, but may vary in size, shape, and other characteristics. In addition, an end of a mold piece may be flat, curved or rounded, and may make an angle or comprise surfaces making different angles with respect to the longitudinal axis of the bore of the piece, effective to form a mold chamber shaped to produce desired taper sections in balloons formed within the mold.
It will be understood that the chambers formed by the adjustable length mold assemblies of the invention provide wall surfaces effective to shape and form balloons of desired shapes and sizes when parisons of suitable composition are placed therein and heated, subjected to tension, filled with pressurized gas, and or subjected to other treatments effective to aid in the formation of balloons. Adjustable length mold assemblies of the invention are suitable for formation of balloons comprising desired shaft sizes and lengths, taper shapes and sizes, and working sections of desired length, diameter, and wall thickness.
The mold pieces of the invention may further be configured to operably connect to detachable extension shafts to connect the mold pieces to a blow-molding machine. Any suitable connection is effective to operably connect the extension shafts. Such suitable connections include pressure fittings such as luer-lock fittings, clamps, o-ring fittings, and the like and mechanical fittings such as threaded couplings, screw fittings, and snap fittings. The molds of the invention may be formed of any suitable material. In particular, the molds may comprise a metal, preferably stainless steel, for ease of fabrication, to achieve good surface quality and temperature and corrosion resiliency.
The present invention further provides a method of forming a variable length mold is provided, comprising providing an outer mold part, an inner mold part, and inserting the inner mold part at least partially within the outer mold part. Further, the invention provides a method for forming an inflatable member, the method comprising providing an adjustable length mold assembly of the invention, positioning an inner piece of the mold within the bore of an outer part, placing a parison of heat-sensitive material within the chamber, connecting the parison to a source of pressure, heating the parison, effective to soften the parison, providing pressure to the parison, effective to raise the pressure within the parison, whereby the heat-sensitive material is deformed and contacts the chamber, effective to form an inflatable member.
Use of the adjustable length mold assemblies of the invention makes it possible to rapidly, simply, and economically shift production from one balloon design to another, provides the ability to simply and quickly modify the balloon design that is produced by a mold, and readily allows for the production, by a single mold, of a variety of similar balloons that vary only in the length of one particular section, such as the length of the working section. The manufacture of inflatable members with a variety of working lengths, for example, while other parameters are the same, allows for balloons to be manufactured to more exacting working length specifications, provides more reproducible angle and diameter measurements, and affords lesser lot variability than other methods. Thus, the invention provides the advantages of greater flexibility in the manufacture of inflatable members, and of the ability to rapidly and economically alter the design of balloon members produced by a mold.